EFA with fixed number of factors

Hi everybody,
I few days ago I posted the following question in another section of the Forum but didn't get any answer. I thought I might have asked it in the wrong section. So I post it here again. I'll be very grateful if you answer.

When should one use exploratory factor analysis with a fixed number of factors?
If we know a priori the number of factors, then we use confirmatory factor analysis (CFA).
On what basis do we decide if we need EFA with a fixed number of factors or CFA?